The collection of leaves, grass clippings and other organic debris from lawn mowers into flexible collection bags is well known, and like vacuum cleaners, these collection bags rely on the porosity of woven fabric bags to exhaust the airstream carrying the debris after it is deposited in the bag. High volume lawn tractor mowers often collect the organic debris in collectors carried on a towed trailer, such as the large volume collector bags disclosed in my co-pending patent application. Even if such collector bags are made of tightly woven fabrics with minimum porosity, they may have mesh screen panels allowing exhaust air to escape after depositing entrained debris.
Fine particles and lighter weight pieces of leaves, grass clippings and other organic debris tend to clog the pores of woven fabric bags, and the pressure differential between the blower-driven internal bag inflation pressure and the external ambient atmosphere drives leaves and grass clippings against the interior surface of any mesh vent and plasters them there, partially embedded or caught in the mesh impeding the escape of exhaust air after it has delivered debris to the bag's interior. The resulting back pressure tends to resist delivery and deposit of more debris.